Current government guidelines recommend that adults engage in 30 minutes of moderate intensity physical activity for most days of the week. To better understand the potential health benefits of physical activity that exceed current guidelines, we propose to examine the relation of physician-supplied coronary heart disease (CHD) risk factor measurements to the amount and intensity of physical activity in 17,287 runners (13,595 male, 3,692 female) who completed a two-page physical activity questionnaire. Data from 9,125 runners are entered and verified into the database, data from an additional 8,162 runners are entered but require verification. The data set constitutes the largest existing sample of runners lipoprotein measurements, larger in fact than the combined total of all previously published studies of HDL-cholesterol in runners. Previous analyses of these data have demonstrated substantial CHD risk factor improvements through running at least 40 miles per week. The small grant award will enable us to assess further the importance of exercise intensity and the mitigating influences of age, diet, adiposity, and medication use. Specific objectives are to: 1)Assess whether running intensity affects CHD risk factors when adjusted for running mileage. Current guidelines state that the benefits of physical activity depend principally on the total amount of activity rather than intensity. 2)Assess whether the relationships between running mileage, running intensity and CHD risk factor levels are affected by age, diet, current adiposity, or medication use. 3)Assess whether running prevents women's middle-aged weight gain and weight retention after pregnancy. (We have shown that men have a propensity to gain weight and intra-abdominal fat at all running mileages unless weekly distance run is increased annually). Statistical power calculations (alpha:=O.05,beta=O.2,2-tailed test) suggest that the hypothesized exercise effects should be detectable. The data were collected as part of the $50,00() Shannon Award to Dr. Williams for the purpose of recruiting runners for a detailed study of lipoproteins. None of the hypotheses of this small grant proposal overlap with the aims of the Shannon Award, and there are no funds available for the further analysis of these data. The results are directly relevant to the exercise habits of the estimated eighteen million Americans who run or jog for health.